chore(gax): resolve linter warnings in apiCallable unit tests

[shivanee-p]

Update Promises in apiCallable.ts to use modern async/await patterns

[gemini-code-assist]

Code Review

This pull request refactors several unit tests in apiCallable.ts to use async/await syntax instead of callbacks and promise chains, improving readability and modernizing the test suite. The review feedback focuses on simplifying the assert.rejects assertions by passing the promises directly rather than wrapping them in redundant async functions, utilizing error constructors for type assertions, and removing unnecessary non-null assertion operators.

[gemini-code-assist]

Node's assert.rejects accepts a Promise directly as its first argument. Wrapping the promise in an async function is redundant and can be simplified.

    await assert.rejects(
      promise,
      (err: GoogleError) => {
        assert(err instanceof GoogleError);
        assert.strictEqual(err.code, status.CANCELLED);
        return true;
      },
    );

[gemini-code-assist]

Node's assert.rejects accepts a Promise directly as its first argument. Wrapping the promise in an async function is redundant and can be simplified.

    await assert.rejects(promise);

[gemini-code-assist]

Node's assert.rejects accepts a Promise directly as its first argument, and can also accept an error constructor (like Error) as the second argument to assert the type of the rejected error. This simplifies the assertion significantly.

    await assert.rejects(promise, Error);

[gemini-code-assist]

Node's assert.rejects accepts a Promise directly as its first argument. Additionally, since err is typed as GoogleError (which is non-nullable), the non-null assertion operator (!) is redundant and can be removed.

    await assert.rejects(
      apiCall({}, undefined),
      (err: GoogleError) => {
        assert(err instanceof Error);
        assert.strictEqual(err.code, FAKE_STATUS_CODE_1);
        assert(err.note);
        const now = new Date();
        assert(
          now.getTime() - startTime.getTime() >= backoff.totalTimeoutMillis!,
        );
        const callsLowerBound =
          backoff.totalTimeoutMillis! /
          (backoff.maxRetryDelayMillis + backoff.maxRpcTimeoutMillis!);
        const callsUpperBound =
          backoff.totalTimeoutMillis! / backoff.initialRetryDelayMillis;
        assert(spy.callCount > callsLowerBound);
        assert(spy.callCount < callsUpperBound);
        return true;
      },
    );